1. Field of the Invention
This invention relates generally to an industrial process and, more particularly, to a method and apparatus for integrating dispatch and process control actions in a semiconductor fabrication process.
2. Description of the Related Art
There is a constant drive within the semiconductor industry to increase the quality, reliability and throughput of integrated circuit devices, e.g., microprocessors, memory devices, and the like. This drive is fueled by consumer demands for higher quality computers and electronic devices that operate more reliably. These demands have resulted in a continual improvement in the manufacture of semiconductor devices, e.g. transistors, as well as in the manufacture of integrated circuit devices incorporating such transistors. Additionally, reducing the defects in the manufacture of the components of a typical transistor also lowers the overall cost per transistor as well as the cost of integrated circuit devices incorporating such transistors.
Generally, a set of processing steps is performed on a lot of wafers using a variety of process tools, including photolithography steppers, etch tools, deposition tools, polishing tools, rapid thermal process tools, implantation tools, etc. The technologies underlying semiconductor process tools have attracted increased attention over the last several years, resulting in substantial refinements. However, despite the advances made in this area, many of the process tools that are currently commercially available suffer certain deficiencies. In particular, such tools often lack advanced process data monitoring capabilities, such as the ability to provide historical parametric data in a user-friendly format, as well as event logging, real-time graphical display of both current processing parameters and the processing parameters of the entire run, and remote, i.e., local site and worldwide, monitoring. These deficiencies can engender non-optimal control of critical processing parameters, such as throughput, accuracy, stability and repeatability, processing temperatures, mechanical tool parameters, and the like. This variability manifests itself as within-run disparities, run-to-run disparities and tool-to-tool disparities that can propagate into deviations in product quality and performance, whereas an ideal monitoring and diagnostics system for such tools would provide a means of monitoring this variability, as well as providing means for optimizing control of critical parameters.
One technique for improving the operation of a semiconductor processing line includes using a factory wide control system to automatically control the operation of the various process tools. The manufacturing tools communicate with a manufacturing framework or a network of processing modules. Each manufacturing tool is generally connected to an equipment interface. The equipment interface is connected to a machine interface that facilitates communications between the manufacturing tool and the manufacturing framework. The machine interface can generally be part of an advanced process control (APC) system. The APC system initiates a control script based upon a manufacturing model, which can be a software program that automatically retrieves the data needed to execute a manufacturing process. Often, semiconductor devices are staged through multiple manufacturing tools for multiple processes, generating data relating to the quality of the processed semiconductor devices.
During the fabrication process various events may take place that affect the performance of the devices being fabricated. That is, variations in the fabrication process steps result in device performance variations. Factors, such as feature critical dimensions, doping levels, contact resistance, particle contamination, etc., all may potentially affect the end performance of the device. Various tools in the processing line are controlled in accordance with performance models to reduce processing variation. Commonly controlled tools include photolithography steppers, polishing tools, etching tools, and deposition tools. Pre-processing and/or post-processing metrology data is supplied to process controllers for the tools. Operating recipe parameters, such as processing time, are calculated by the process controllers based on the performance model and the metrology information to attempt to achieve post-processing results as close to a target value as possible. Reducing variation in this manner leads to increased throughput, reduced cost, higher device performance, etc., all of which equate to increased profitability.
Target values for the various processes performed are generally based on design values for the devices being fabricated. For example, a particular process layer may have a target thickness. Operating recipes for deposition tools and/or polishing tools may be automatically controlled to reduce variation about the target thickness. In another example, the critical dimensions of a transistor gate electrode may have an associated target value. The operating recipes of photolithography tools and/or etch tools may be automatically controlled to achieve the target critical dimensions.
Typically, a control model is used to generate control actions for changing the operating recipe settings for a process tool being controlled based on feedback or feedforward metrology data collected related to the processing by the process tool. To function effectively, a control model must be provided with metrology data in a timely manner and at a quantity sufficient to maintain its ability to predict the future operation of the process tool it controls.
In a fabrication facility, a dispatch system is provided for scheduling wafers through the required process and metrology steps. The dispatch system seeks to optimize tool utilization and provide a smooth flow of product through the fabrication facility. Typically, the dispatch system uses a priority system that gives higher priority lots preferred access to the various tools. Priorities may be determined based on factors such as device type, anticipated performance, business goals, etc.
Activities in a fabrication facility are typically conducted in a non-sequential fashion. For example, lots are typically not measured in the order they are processed. Because the process control and dispatch systems are constructed with different goals in mind, the scheduling performed by the dispatch system may not result in the generation of the data desired for effective operation of the process control system. For example, the process control system may desire a schedule that interrupts the smooth flow of products, while the dispatch system may prioritize lots in such a way reduces the effectiveness of process control.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
One aspect of the present invention is seen in a method that includes scheduling a plurality of workpieces for processing by a plurality of tools. Each workpiece has an associated priority. The processing in at least one of the tools is controlled in accordance with a process control model. A process control request associated with the controlling of the tool is generated. The priorities of at least a subset of the workpieces are determined based on the process control request.
Another aspect of the present invention is seen in a manufacturing system including a plurality of tools for processing workpieces, a dispatch unit, and a process control unit. The dispatch unit is configured to schedule a plurality of workpieces for processing by the tools. Each workpiece has an associated priority. The process control unit is configured to control the processing in at least one of the tools in accordance with a process control model and generate a process control request associated with the controlling of the tool. The dispatch unit is further configured to receive the process control request and determine the priorities of at least a subset of the workpieces based on the process control request.